yaml复制代码routes:
  - id: router1
    uri: http://www.baidu.com
    predicates:
      - Path=/baidu/**
    filters:
      - StripPrefix=1

yaml复制代码      routes:
      - id: demo
        uri: http://demo
        predicates:
        - Path=/demo/**
        filters:
        - StripPrefix=1

java复制代码this.rmContext = new RMContextImpl()

java复制代码loadConfigurationXml(YarnConfiguration.CORE_SITE_CONFIGURATION_FILE);

java复制代码loadConfigurationXml(YarnConfiguration.YARN_SITE_CONFIGURATION_FILE);

java复制代码this.rmContext.setHAEnabled(HAUtil.isHAEnabled(this.conf));

java复制代码rmDispatcher = setupDispatcher();
addIfService(rmDispatcher);
rmContext.setDispatcher(rmDispatcher);

java复制代码adminService = createAdminService();
addService(adminService);
rmContext.setRMAdminService(adminService);

java复制代码if (this.rmContext.isHAEnabled()) {
        /**
         *      yarn.resourcemanager.ha.automatic-failover.emabled = true
         *      yarn.resourcemanager.ha.automatic-failover.embedde = true
         *      embedde = true 表明使用原生的zookeeperAPI来执行选举 否则使用curator框架来实现
         *      不同点：zookeeperAPI复杂一点
         */
      if (HAUtil.isAutomaticFailoverEnabled(conf)
          && HAUtil.isAutomaticFailoverEmbedded(conf)) {
          //创建选举器 ActiveStandbyElectorBasedElectorService
          // 阻塞的进行最大三次的尝试选举 不成功交给线程
        EmbeddedElector elector = createEmbeddedElector();
        addIfService(elector);
        rmContext.setLeaderElectorService(elector);
      }
    }

java复制代码createAndInitActiveServices

java复制代码super.serviceInit(this.conf);

java复制代码createEmbeddedElector(){
    if (curatorEnabled) {
          this.zkManager = createAndStartZKManager(conf);
          elector = new CuratorBasedElectorService(this);
        } else {
          elector = new ActiveStandbyElectorBasedElectorService(this);
        }
}

java复制代码String zkQuorum = conf.get(YarnConfiguration.RM_ZK_ADDRESS);

java复制代码String rmId = HAUtil.getRMHAId(conf);
String clusterId = YarnConfiguration.getClusterId(conf);

java复制代码localActiveNodeInfo = createActiveNodeInfo(clusterId, rmId);

java复制代码String zkBasePath = conf.get(YarnConfiguration.AUTO_FAILOVER_ZK_BASE_PATH,YarnConfiguration.DEFAULT_AUTO_FAILOVER_ZK_BASE_PATH);
String electionZNode = zkBasePath + "/" + clusterId;

java复制代码int maxRetryNum =
        conf.getInt(YarnConfiguration.RM_HA_FC_ELECTOR_ZK_RETRIES_KEY, conf
        .getInt(CommonConfigurationKeys.HA_FC_ELECTOR_ZK_OP_RETRIES_KEY,
        CommonConfigurationKeys.HA_FC_ELECTOR_ZK_OP_RETRIES_DEFAULT));

java复制代码elector = new ActiveStandbyElector(zkQuorum, (int) zkSessionTimeout,electionZNode, zkAcls, zkAuths, this, maxRetryNum, false);

java复制代码elector.ensureParentZNode();

java复制代码super.serviceInit(conf)

java复制代码protected void createAndInitActiveServices(boolean fromActive) {
    activeServices = new RMActiveServices(this);
    activeServices.fromActive = fromActive;
    activeServices.init(conf);
  }

java复制代码standByTransitionRunnable = new StandByTransitionRunnable();

ini复制代码rmSecretManagerService = createRMSecretManagerService();
addService(rmSecretManagerService);

ini复制代码containerAllocationExpirer = new ContainerAllocationExpirer(rmDispatcher);

java复制代码scheduler = createScheduler();

java复制代码rmDispatcher.register(SchedulerEventType.class, schedulerDispatcher);
// Register event handler for RmAppEvents
rmDispatcher.register(RMAppEventType.class,
          new ApplicationEventDispatcher(rmContext));
// Register event handler for RmAppAttemptEvents
rmDispatcher.register(RMAppAttemptEventType.class,
          new ApplicationAttemptEventDispatcher(rmContext));
// Register event handler for RmNodes
rmDispatcher.register(
          RMNodeEventType.class, new NodeEventDispatcher(rmContext));

java复制代码if (this.rmContext.isHAEnabled()) {
  transitionToStandby(false);
}

java复制代码startWepApp();
if (getConfig().getBoolean(YarnConfiguration.IS_MINI_YARN_CLUSTER,
    false)) {
  int port = webApp.port();
  WebAppUtils.setRMWebAppPort(conf, port);
}

java复制代码super.serviceStart();

java复制代码if (!this.rmContext.isHAEnabled()) {
  transitionToActive();
}

java复制代码EmbeddedElector elector = createEmbeddedElector();
addIfService(elector);
rmContext.setLeaderElectorService(elector);

cpp复制代码typedef struct {
  A_char*    messageZ;
  PF_FpLong  big_numF;
  void*      temp_storage;
} non_flat_data;

typedef struct {
  char       message[256];
  PF_FpLong  big_numF;
  A_Boolean  big_endianB;
} flat_data;

cpp复制代码PF_Err(*PF_GetConstSequenceData)(
  PF_ProgPtr effect_ref,
  PF_ConstHandle *sequence_data);

cpp复制代码static PF_Err Render(
   PF_InData   *in_dataP,
   PF_OutData  *out_dataP,
   PF_ParamDef *params[],
   PF_LayerDef *output )
{
    PF_ConstHandle seq_handle;

    AEFX_SuiteScoper<PF_EffectSequenceDataSuite1> seqdata_suite = ///< 获取套件
      AEFX_SuiteScoper<PF_EffectSequenceDataSuite1>(
        in_dataP,
        kPFEffectSequenceDataSuite,
        kPFEffectSequenceDataSuiteVersion1,
        out_dataP);

    PF_ConstHandle const_seq; ///< 只读对象
    seqdata_suite->PF_GetConstSequenceData(in_data->effect_ref, &const_seq);
 ​
    // 将 const_seq 转换为存储到 sequence_data 时使用的类型

    // rest of render function code...
}

arduino复制代码输入： digits = "23"
输出： ["ad","ae","af","bd","be","bf","cd","ce","cf"]

ini复制代码输入： digits = ""
输出： []

arduino复制代码输入： digits = "2"
输出： ["a","b","c"]

c++复制代码class Solution
{
public:

    vector<string> letterCombinations(string digits)
    {
        // 如果字符串为空，直接返回
        if (digits == "")
        {
            return result;
        }
        // 进行回溯处理
        backtracking(digits,0);
        return result;
    }

private:
    // 结果集
    vector<string> result;
    // 记录叶子节点
    string s;
    // 定义数字和字符串的映射
    // 采用字符串数组来存储
    const string letterMap[10] = {
        "",     //0
        "",     //1
        "abc",  //2
        "def",  //3
        "ghi",  //4
        "jkl",  //5
        "mno",  //6
        "pqrs", //7
        "tuv",  //8
        "wxyz", //9

    };
    // 这里的index不是 组合问题里面的 startIndex
    // index指向数字，表示遍历到第几个数字了，还表示树的深度
    void backtracking(const string &digits, int index)
    {
        // index等于字符串的大小时
        // 说明找到了匹配的，添加到结果集中
        if (index == digits.size())
        {
            result.push_back(s);
            return;
        }

        // 将index指向的数字转换成int类型
        int digit = digits[index] - '0';
        // 取出数字对应的字符串
        string letter = letterMap[digit];
        // 对字符串进行遍历
        for (int i = 0; i < letter.size(); i++)
        {
            s.push_back(letter[i]);
            // 下一层处理下一个数字
            backtracking(digits, index + 1);
            s.pop_back(); // 回溯
        }
    }
};

ini复制代码输入： n = 4, k = 2
输出：
[
  [2,4],
  [3,4],
  [2,3],
  [1,2],
  [1,3],
  [1,4],
]

lua复制代码输入： n = 1, k = 1
输出： [[1]]

c++复制代码class Solution
{
public:
    vector<vector<int>> combine(int n, int k)
    {
        backtracking(n, k, 1);
        return result;
    }

private:
    // 使用两个全局变量存放结果
    // 存放最终的结果
    vector<vector<int>> result;
    // 存放单层递归的结果
    vector<int> path;

    // 回溯算法
    // startIndex用来控制开始遍历的索引，遍历的范围逐渐缩小
    void backtracking(int n, int k, int startIndex)
    {
        // 递归的终止条件
        // 当path的 大小等于 k 时，将path数据存入到 结果数组中
        if (path.size() == k)
        {
            result.push_back(path);
            return;
        }

        // 单层递归逻辑
        for (int i = startIndex; i <= n; i++)
        {
            path.push_back(i); // 处理节点
            // 递归处理，控制树的纵向遍历
            backtracking(n, k, i + 1);
            path.pop_back(); // 回溯，撤销处理的节点
        }
    }
};

c++复制代码for(int i = startIndex;i<=n-(k-path.size())+1;i++)
{
    ... ...
}

lua复制代码输入: k = 3, n = 7
输出: [[1,2,4]]

ini复制代码输入: k = 3, n = 9
输出: [[1,2,6], [1,3,5], [2,3,4]]

c++复制代码class Solution
{
public:
    vector<vector<int>> combinationSum3(int n, int k)
    {
        backtracking(n, k, 1);
        return result;
    }

private:
    vector<vector<int>> result;
    vector<int> path;

    // 使用减法逐步减小n的值
    void backtracking(int n, int k, int startIndex)
    {
        // 剪枝操作
        if (n < 0)
        {
            return;
        }
        // 如果path的大小满足条件，并且path中的和为 n
        if (path.size() == k && n == 0)
        {
            result.push_back(path);
            return;
        }

        for (int i = startIndex; i <= 9; i++)
        {
            // 每次遍历到一个数，就将n的值减去这个数
            n -= i;
            // 将 i 添加到 path 中
            path.push_back(i);
            // 递归处理
            backtracking(n, k, i + 1);
            n += i;          // 回溯
            path.pop_back(); // 回溯
        }
    }
};

scss复制代码Index 获取树节点在树节点集合中的位置
Nodes 获取分配给树视图控件的树节点集合
Parent 获取或设置控件的父容器
SelectedNode 获取或设置当前在树视图控件中选定的树节点
ExpandAll 展开所有树节点
Checked 获取或设置一个值，用以指示树节点是否处于选中状态
Text 获取或设置在树节点标签中显示的文本
Expand 展开树节点
Clear 清空树
Remove 从树视图控件中移除当前树节点。

csharp复制代码using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace TreeTest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            TreeNode treeNode = new TreeNode(textBox1.Text, 2, 2);
            treeView1.Nodes.Add(treeNode);
            treeView1.Select();
        }

        private void treeView1_AfterSelect(object sender, TreeViewEventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)
        {
            TreeNode selectdnode = treeView1.SelectedNode;
            if(selectdnode!=null)
            {
                TreeNode chnode = new TreeNode(textBox2.Text, 2, 2);
                selectdnode.Nodes.Add(chnode);
                selectdnode.Expand();
                treeView1.Select();
            }
            else
            {
                MessageBox.Show("请选择需要添加子节点");
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {
            TreeNode selectnode = treeView1.SelectedNode;
            TreeNode parentnode = selectnode.Parent; 
            if(parentnode == null)
            {
                treeView1.Nodes.Remove(selectnode);
            }
            else
            {
                parentnode.Nodes.Remove(selectnode);
            }
            treeView1.Select();
        }

        private void button4_Click(object sender, EventArgs e)
        {
            treeView1.Nodes.Clear();
        }

        private void button5_Click(object sender, EventArgs e)
        {
            this.textBox1.Clear();
            this.textBox2.Clear();
        }
    }
}

csharp复制代码输入： [4,1,6,0,2,5,7,null,null,null,3,null,null,null,8]
输出： [30,36,21,36,35,26,15,null,null,null,33,null,null,null,8]

ini复制代码输入： root = [0,null,1]
输出： [1,null,1]

ini复制代码输入： root = [1,0,2]
输出： [3,3,2]

ini复制代码输入： root = [3,2,4,1]
输出： [7,9,4,10]

c++复制代码class Solution
{
public:
    TreeNode *convertBST(TreeNode *root)
    {
        // 第一次遍历，求出所有节点值的累加和
        traversal(root);
        // 第二次遍历，更新节点的累加和
        changeVal(root);
        // 返回根节点
        return root;
    }

private:
    int sum;                            // 记录所有节点值的累加和
    TreeNode *preOld = new TreeNode(0); // 记录前驱节点的旧值
    TreeNode *preNew = NULL;            // 记录前驱节点的新值
    TreeNode *tmp = new TreeNode(0);    // 临时节点，记录当前节点的旧值

    // 第一次中序遍历，求节点值累加和
    void traversal(TreeNode *cur)
    {
        if (cur == NULL)
        {
            return;
        }
        // 左
        if (cur->left)
        {
            traversal(cur->left);
        }

        // 中
        sum += cur->val;

        // 右
        if (cur->right)
        {
            traversal(cur->right);
        }
    }

    // 第二次中序遍历，修改节点的值
    void changeVal(TreeNode *cur)
    {
        if (cur == NULL)
        {
            return;
        }

        // 左
        if (cur->left)
        {
            changeVal(cur->left);
        }

        // 中
        if (preNew == NULL)
        {
            // 当前驱节点指向空时，找到左子树的最左叶子节点
            preOld->val = cur->val; // 记录旧值
            cur->val = sum;         // 更新值
            preNew = cur;           // 更新前驱节点指针
        }
        else
        {
            tmp->val = cur->val;                  // 记录当前节点的旧值
            cur->val = preNew->val - preOld->val; // 更新当前节点的值
            preOld->val = tmp->val;               // 更新前驱节点旧值
            preNew = cur;                         // 更新前驱节点
        }

        // 右
        if (cur->right)
        {
            changeVal(cur->right);
        }
    }
};

c++复制代码class Solution
{
public:
    TreeNode *convertBST(TreeNode *root)
    {
        traversal(root);
        return root;
    }

private:
    TreeNode *pre = new TreeNode(0); // 前驱节点值初始为0
    void traversal(TreeNode *cur)
    {
        if (cur == NULL)
        {
            return;
        }

        // 右
        if (cur->right)
        {
            traversal(cur->right);
        }

        
        // 当前节点的值等于前一个节点的值+当前节点的值
        cur->val = pre->val + cur->val;
        pre = cur;
        // 左
        if (cur->left)
        {
            traversal(cur->left);
        }
    }
};

php复制代码<?php

namespace App\Http\Controllers\Web;

use App\Http\Controllers\BaseController;
use App\Models\Cart;
use App\Models\Order;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\DB;

class OrderController extends BaseController
{
	/**
     * 订单列表
     */
    public function index(Request $request) {
        // 状态查询
        $status = $request->query('status') ;

        // 根据标题
        $title = $request->query('title');

        $order = Order::where('user_id', auth('api')->id())
            ->when($status, function ($query) use ($status) {
                $query->where('status', $status);
            })
            ->when($status, function ($query) use ($title) {
                $query->whereHas('goods', function ($query) use($title) {
                    $query->where('title', 'like', "%{$title}%");
                }); // 向关联加入自定义约束
            })
            ->paginate(3);
        return $this->response->paginator($order, new OrderTransformer());
    }
	
    /**
     * 预览订单
     */
    public function preview()
    {
        // 地址数据
        // TODO 暂时模拟地址数据
        $address = [
            ['id' => 1, 'name' => '张三', 'address' => '厦门', 'phone' => '123123'],
            ['id' => 2, 'name' => '李四', 'address' => '厦门', 'phone' => '123123'],
            ['id' => 3, 'name' => '王武', 'address' => '厦门', 'phone' => '123123'],
        ];

        // 购物车数据
        $carts = Cart::where('user_id', auth('api')->id())
            ->where('is_checked', 1)
            ->with('goods:id,cove,title')
            ->get();

        // 返回数据
        return $this->response->array([
            'address' => $address,
            'carts' => $carts,
        ]);
    }

    /**
     * 提交订单
     */
    public function store(Request $request)
    {
        // 验证地址字段
        $request->validate([
            'address_id' => 'required' // TODO 地址要存在才行 exists:addresses,id
        ], [
            'address_id.required' => ['收获地址不能为空']
        ]);

        // 处理插入的数据
        $user_id = auth('api')->id();
        $order_no = date('YmdHis') . rand(100000, 999999);
        $amount = 0;
        $cartsQuery = Cart::where('user_id', $user_id)
            ->where('is_checked', 1);

        $carts = $cartsQuery->with('goods:id,price')->get();

        // 要插入的订单详情的数据
        $insertData = [];


        foreach ($carts as $key => $cart) {
        	// 如果有商品库存不足，提示用户重新选择
            if ($cart->goods->stock < $cart->num) {
                return $this->response->errorBadRequest($cart->goods->title.' 库存不足，请重新选择商品！');
            }
            $insertData[] = [
                'goods_id' => $cart->goods_id,
                'price' => $cart->goods->price,
                'num' => $cart->num
            ];
            $amount += $cart->goods->price * $cart->num;
        }

        try {
            DB::beginTransaction(); // 开启事务
            // 生成订单
            $order = Order::create([
                'user_id' => $user_id,
                'order_no' => $order_no,
                'address_id' => $request->input('address_id'),
                'amount' => $amount
            ]);

            // 生成订单的详情
            $order->orderDetails()->createMany($insertData);

            // 删除已经结算的购物车数据
            $cartsQuery->delete();
            
            // 减去商品对应的库存量
            foreach($carts as $cart) {
                Good::where('id', $cart->goods_id)->decrement('stock', $cart->num);
            }
            DB::commit(); // 没有异常才提交
            return $this->response->created();
        } catch (\Exception $e) {
            DB::rollBack(); // 出现异常 事务 数据回滚
            throw $e; // 抛出异常
        }
    }
    // 订单详情
    public function show(Order $order) {
        return $this->response->item($order, new OrderTransformer());
    }
	/**
     * 确认收货
     */
    public function confirm(Order $order) {
        if ($order->status != 3) {
            return $this->response->errorBadRequest('订单状态异常！');
        }
       try {
            DB::beginTransaction();
            $order->status = 4;
            $order->save();

            $orderDetails = $order->orderDetails;
            
            // 增加订单下所有商品的销量
            foreach($orderDetails as $orderDetail) {
                // 更新商品销量
                Good::where('id', $orderDetail->goods_id)->increment('sales', $orderDetail->num);
            }

            DB::commit();
        } catch (\Exception $e) {
            DB::rollBack();
            throw $e;
        }
        return $this->response->noContent();
    }
}

php复制代码    /**
     * 订单远程一对多，关联商品
     */
    public function goods() {
        return $this->hasManyThrough(
            Good::class, // 最终关联的模型
            OrderDetails::class, // 中间模型
            'order_id', // 中间模型和本模型关联的外键
            'id', // 最终关联模型的外键
            'id', // 本模型和中间模型关联的健
            'goods_id' // 中间表和最终模型关联到一个键
        );
    }

php复制代码    /**
     * 商品数据
     */
    public function includeGoods(Order $order) {
        return $this->collection($order->goods, new GoodTransformer());
    }

php复制代码// 定时检测订单状态，超过10分钟未支付的，作废
        // 真是项目一般会采用长链接，因为可以实时长链接，时间一到，直接作废，而任务调度的话不会那么精确的跟前端显示一样的时间
        // 任务调度的话 在一定的时间帮我们去执行任务 像备份数据...
        $schedule->call(function () {
            // info('hellp');
            $orders = Order::where('status', 1)
                    ->where('created_at', '<', date('Y-m-d H:i:s', time()-600))
                    ->with('orderDetails.goods') // 拿到关联的商品
                    ->get();

            // 循环订单，修改订单状态，还原商品库存
            try {
                DB::beginTransaction(); // 开启门面

                foreach($orders as $order) {
                    $order->status = 5;
                    $order->save();

                    // 还原商品库存
                    foreach($order->orderDetails as $details) {
                        $details->goods->increment('stock', $details->num);
                    }
                }

                Db::commit();
            } catch (\Exception $e) {
                DB::rollBack();
                Log::error($e);
            }

        })->everyMinute();

php复制代码        /**
         * 订单
         */
        // 订单预览页
        $api->get('order/preview', [OrderController::class, 'preview']);

        // 提交订单
        $api->post('order', [OrderController::class, 'store']);

		// 订单详情
        $api->get('order/{order}', [OrderController::class, 'show']);

		// 订单列表
        $api->get('orders', [OrderController::class, 'index']);
		
		// 确认收货
        $api->patch('orders/{order}/confirm', [OrderController::class, 'confirm']);

js复制代码package main

import (
   "fmt"
   "github.com/Shopify/sarama"
   cluster "github.com/bsm/sarama-cluster"
   "time"
)

var (
   Consumer *cluster.Consumer
   producer sarama.SyncProducer
   brokers = []string{"ip1:9092","ip2:9092","ip3:9092"}
   topic = "testGo"
   groupId = "testGo_test1"
)

func initProducer() {
   var err error
   config := sarama.NewConfig()
   config.Producer.RequiredAcks = sarama.WaitForLocal
   config.Producer.Retry.Max = 3
   config.Producer.Return.Successes = true
   brokers := brokers
   producer, err = sarama.NewSyncProducer(brokers,config)
   if err != nil {
      fmt.Printf("生产者初始化失败 -> %v \n", err)
      panic(err)
   }
   fmt.Println("生产者初始化成功。")
}

func initConsumer()  {
   var err error
   config := cluster.NewConfig()
   config.Consumer.Group.Rebalance.Strategy = sarama.BalanceStrategyRange
   config.Consumer.Offsets.Initial = sarama.OffsetNewest
   Consumer, err = cluster.NewConsumer(brokers,groupId,[]string{topic},config)
   if err != nil {
      fmt.Printf("消费者初始化失败 -> %v \n", err)
      panic(err.Error())
   }
   if Consumer == nil {
      panic(fmt.Sprintf("消费者为空. kafka info -> {brokers:%v, topic: %v, group: %v}", brokers, topic, groupId))
   }
   fmt.Printf("消费者初始化成功, consumer -> %v, topic -> %v, ", Consumer, topic)
}

func main() {
   initProducer()
   initConsumer()

   //生产消息
   for i := 1;i < 100; i ++ {
      pid, offset, err := producer.SendMessage(&sarama.ProducerMessage{
         Topic:     topic,
         Key:       sarama.StringEncoder(i),
         Value:     sarama.ByteEncoder("this is test message."),
      })
      if err != nil {
         fmt.Println("发送消息失败, err:", err)
         return
      }
      fmt.Printf("offset: %v\n", offset)
   }
   
   time.Sleep(2 * time.Second)

   //消费消息
   for {
       select {
       case msg, ok := <-Consumer.Messages():
           if ok {
              fmt.Printf("kafka msg: %s \n", msg.Value)
           }
      }
   }
}

ini复制代码var emptyList =[];

var nameList = ['jack','mac'];

ini复制代码var nameList = List.filled(2, 'max');

csharp复制代码nameList.add('tony');
nameList.addAll(['lili', 'bruce']);

ini复制代码nameList.removeAt(0);
nameList.clear();

css复制代码var names = ['jack', 'tony', 'max'];

fruits.sort((a, b) => a.compareTo(b));

ini复制代码var names = <String>[];

names.add('jack');

csharp复制代码//创建一个空的set
var names = <String>{};

// 添加新的元素
names.addAll(['jack', 'tony', 'max']);

//删除元素

names.remove('jack');

ini复制代码var names = Set.from(['jack', 'tony', 'max']);

java复制代码assert(names.contains('jack'));

assert(names.containsAll(['jack', 'tony']));

ini复制代码var name1 = Set<String>();
name1.addAll(['jack', 'tony', 'max']);

var name2 = Set.from(['tony', 'bily']);
var intersection = name1.intersection(name2);

javascript复制代码// 创建map
var studentMap = {
  'name': 'jack',
  'age': '18',
  'class': 'class one'
};


var teacherMap = Map();

var teacherMap2 = Map<String, String>();

javascript复制代码  var studentMap =Map();
  studentMap.putIfAbsent('name', ()=>'jack');
  studentMap.remove('name');

java复制代码assert(studentMap.containsKey('name'));

scss复制代码assert(studentMap.isEmpty);
assert(studentMap.isNotEmpty);

ini复制代码var names = ['jack', 'bob', 'tom'];

names.forEach((name) => print('the name is $name'));

var nameMap = {};

nameMap.forEach((k, v) {
});

ini复制代码var names = ['jack', 'bob', 'mark'];

var names2 = names.map((name) => name.toUpperCase());

ini复制代码var names2 =
    names.map((name) => name.toUpperCase()).toList();

ini复制代码var names = ['jack', 'bob', 'max'];

bool hasJack(String name) =>
    name == 'jack';

var seleteJack =
    names.where((name) => hasJack(name));

assert(names.any(hasJack));

assert(!names.every(hasJack));